Generally, as a technology for distilling sea water, there are an evaporation method using an evaporation phenomenon of water, and a membrane filtration method using a membrane. The technology for distilling sea water mainly uses a large-capacity plant of 10,000 tons or more a day, but this kind of plant consumes much energy and uses an energy source relying on fossil fuel. To solve a problem of depletion of fossil fuel and environmental pollution, the technology for distilling sea water also takes into great consideration the use of renewable energies such as solar thermal energy.
Meanwhile, there are many island areas, remote areas, and developing countries which have insufficient power and water supply infrastructures all over the world. These areas require a lot of initial construction cost and maintenance cost and have little operation/maintenance technology, and therefore it is impossible to construct and operate a large-scale distillation plant in these locations. Therefore, in the areas such as the island areas where energy supply and demand conditions are prohibitive and no water supply infrastructure is present, a technology for distilling sea water using renewable energy sources such as solar thermal energy is urgently required.
A solar still has a simple structure, and therefore has been used in the past. However, when evaporating and distilling sea water, solar thermal energy reflected from a sea water surface and emitted to the outside and incident heat energy are used for evaporation only once, and therefore efficiency and productivity may be reduced.
Further, exhaust gas generated from a general power generator is emitted into the air as it is, and waste heat of the exhaust gas may be used as a heat source for distillation.